1. Field of the Invention
The invention relates to a progressive die machine having a quality control feedback apparatus mounted thereto which measures critical dimensions of the part passing through the machine and reconfigures a forming station on the progressive die to compensate for any malformed parts.
2. Description of the Related Art
Progressive die machines have long been known in the art to comprise a fixed lower die and an upper die which is reciprocally movable with respect to the lower die. The upper die is typically slidably mounted within rails which constrain the upper die to vertical movement therein. In addition, a motor having an output shaft is provided. The output shaft typically has a distal end provided with a concentrically-mounted plate thereon which, in turn, has an eccentrically-mounted pin adjacent an outer radial edge thereof. Further, a ram is provided which has one end mounted to an upper surface of the die and an opposite end having a bearing which is journaled to the pin of the motor. Thus, as rotational motion is imparted to the output shaft by the motor, the pin is rotated as well and traces a circular path. As a result, the ram, in conjunction with the upper die, is moved reciprocally within the rails with respect to the lower die.
Each rotation of the output shaft of the motor is referred to as the "stroke" of the machine and ranges between 0 and 360 degrees. Thus, the point at which the pin on the plate of the motor output shaft is located at the uppermost vertical position with respect to the plate is referred to as the 0 degree position or "top dead center" (TDC). At TDC, the upper die is positioned the greatest extent above the lower die. The point at which the pin on the plate of the motor output shaft is located adjacent to the lowermost vertical position with respect to the plate is referred to as the 180 degree position. In the 180 degree position, the upper die is positioned adjacent to the lower die and is the position whereby the forming operations are performed on the web. Between the 0 and 180 degree positions, the upper die is lowered with respect to the lower die and between the 180 and 360 degree positions, the upper die is raised with respect to the lower die.
The upper and lower dies cooperate to define several forming stations therein. Each forming station includes an individual forming tool and a die which are configured and dimensioned so that a particular predetermined operation can be performed on a web fed between the upper and lower dies. The web is typically an elongated strip of material provided as a feedable supply adjacent the machine, such as on a spool. The progressive die machine typically includes a feeding apparatus mounted adjacent the lower die which sequentially advances the web between the upper and lower dies and through each of the forming stations therein.
The number of forming stations is determined by the number of forming operations necessary to form a desired part. A portion of each of the forming tools are located on the upper die and are driven in unison in reciprocal fashion by the ram. Thus, a forming operation is performed at each forming station during each stroke of the ram.
Following each stroke, the web is advanced so that each portion of the web is positioned within the next successive forming station in the machine. When a portion of the web has passed each forming station in the progressive die machine, a desired part is formed. The last station in the machine typically includes a severing tool and a discharge chute. The severing tool cuts the formed part from the web so that the formed part can fall into the discharge chute and be accumulated therein.
The above-described machine typically forms a completed part. However, it has been found that some parts require additional manufacturing operations to be performed thereon before the part is ready for shipping to customers. One such additional operation is the staking of a stud, such as a threaded fastener, into the formed part after it has been completed. Typically, an aperture is provided in the part by the progressive die machine and the stud is located in the aperture after the progressive die machine has completed the forming process. The staking of the stud often requires an additional manufacturing apparatus and/or substantial human intervention to complete the part which can add to the per unit cost of producing the part. Prior art progressive die machines have been insufficient in providing a solution to this problem.
In addition, the formed part may have a geometrical configuration which makes the staking of a stud therein prohibitively difficult. For example, a part can be provided with a C-shaped configuration whereby the stud is desired to be located within an interior surface thereof. Depending upon the clearance provided within the interior surface, it is often difficult to accurately stake the stud therein. Thus, the formed part must either not include the stud or the formed part must be bent to a lesser degree than is required. After the part has been formed by the progressive die machine, the stud must be staked therein by a separate apparatus and process, and then the part must be further bent to place the formed part within required tolerance limits.
Additional problems are encountered by the progressive die machines. Changes in a wide variety of uncontrollable characteristics can cause the formation of parts which do not fall within tolerances required by a particular application for a part. Such tolerances can be of critical importance because a part which falls outside of these tolerances can cause a catastrophic failure in the system or machine in which the part is ultimately installed. Some examples of the uncontrollable characteristics encountered by prior art progressive die machines include: changes in thickness in the web material from which the parts are formed, flaws in the web material, wear on the forming tools and dies and foreign matter located on the web material. These characteristics can cause the formation of unacceptable parts by the progressive die machine which can often go undetected by the machine or its operator during use.